Process for making a video record disc

ABSTRACT

A transparent record disc is provided which may appropriately have video signals optically recorded thereon, the record is composed of a lamination, for example, of pliant transparent plastic on a base of hard transparent plastic. The base provides strength for the record and the pliant plastic permits the video recording to be impressed into the record by simple embossing means, rather than by stamping or molding by which the surface of the record is actually raised above its melting point and caused to flow. An improved process for forming the video recordings on the disc record is also provided.

This application is a continuation of application Ser. No. 936,982,filed 8/25/78, now abandoned, which is a division of application Ser.No. 812,157, filed July 1, 1977, now abandoned, which is a division ofSer. No. 571,259 filed Apr. 24, 1975, now abandoned, which is acontinuation in part of application Ser. No. 735,007 filed June 6, 1968,now abandoned.

RELATED COPENDING APPLICATIONS

Ser. No. 507,474, filed Nov. 12, 1965 now abandoned; Ser. No. 627,701,filed Apr. 3, 1967, now U.S. Pat. No. 3,430,966; and Ser. No. 741,020,filed June 28, 1968, now U.S. Pat. No. 3,530,258.

BACKGROUND OF THE INVENTION

A transparent plastic disc is described in the copending applicationSer. No. 627,701, now U.S. Pat. No. 3,430,966, issued Mar. 4, 1969, inwhich picture information in the form of video signals is recorded onone or both sides of the disc. The recorded picture information on thedisc is intended to be reproduced, for example, through a televisionreceiver, by playing the disc on a turntable and by directing a lightbeam through the disc, as described in the copending application Ser.No. 507,474, now abandoned, and its continuation-in-part application,now U.S. Pat. No. 3,530,258. The light beam is modulated by the videorecordings on the disc, and a pick-up head is provided which responds tothe resulting light signals to transform them into correspondingelectrical video or picture signals for playback purposes.

The present invention is concerned with such a video disc record, andwith a duplication process by which a multiplicity of such records maybe mass-produced from a master record die. The material of the discrecord surface is made such to be appropriate for embossing and toenable, under suitable temperature conditions, a slight force pressingthe disc surface against a master die to cause the impressions on thesurface of the die to be embossed into the surface of the disc. Withsuch an embossing process, there is no transverse flow of the discmaterial, as occurs in the usual prior art stamping or moldingprocesses, as are presently being used in the production of phonographsound records, for example, and by which the actual surface of therecord is raised above its melting point.

The stamping techniques presently being used in the manufacture ofphonograph records are not be suitable for the extraordinarily finemicrogrooves and patterns required by video frequency recordings ofpicture information. Such stamping techniques as are presently beingused in the production of phonograph sound records require that themaster record die be heated to a temperature above the melting point ofthe vinyl or other plastic material used in the phonograph record.

In the prior art phonograph record duplicating process, a "biscuit" ofthe vinyl or other plastic material is placed in a "stamper", and theheated master record die is brought down onto one or both surfaces ofthe biscuit. The plastic of the biscuit surface is melted and caused toflow radially into the spaces defined by the impressions on the masterdie surface. As mentioned above, this stamping technique by present daystandards appears to be unsuited for the extremely fine micro-spiralgrooves required for video frequency recordings.

As an alternative to the present day practice, and as will be described,a video disc record blank of laminated transparent plastic constructionmay be provided, the laminated record having a surface layer ofrelatively soft transparent plastic of any suitable known type, andwhich can be readily embossed; and a supporting base of a rigid plastic,such as an acrylic resin or polyvinyl chloride. As a first step in thealternate approach, the laminated disc record blank is heated to a pointat which the surface tension of the surface material causes the surfaceto be smooth and regular. This temperature is the critical temperatureat which embossed impressions may be formed on the disc surface, and itis below the melting point of the surface material.

The embossing die(s) is (are) heated to a temperature slightly above thecritical temperature, and it (they) and the record blank are broughttogether with a slight pressure. As the die(s) and the record blank arebrought together, the die(s) is (are) cooled to the aforesaid criticaltemperature, and its (their) surface impressions are embossed into thesurface(s) of the record.

Obviously, if two "sides" are being embossed, two embossing dies arerequired. The supporting structure would require modification, but suchmodification is well within the skill of the art.

After the disc record has been embossed, as described above, an opaquemask is deposited into the portions of its surface around the resultingembossed micro-grooves. This latter mask may be formed on the disc byusing a vacuum deposition technique, as will be described.

The aforesaid disc record, when laminated in accordance with theaforesaid alternate approach, is used in order to present the desiredsurface characteristics for optimum embossing capabilities, and yet sothat the record itself may be rugged and suitable for rough usage. Thelaminated structure of the record comprises reasonably tough anddimensionally stable clear plastic for the main body of the disc; and aplastic material on one or both surfaces of the disc which is mostsuited for embossing. The combination provides a video record disc whichis useful, which can take an appropriate amount of handling, and whichstill can be embossed easily and effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective representation of a disc which may beconstructed in accordance with the concepts of the present invention,and by the process to be described, the disc being shown as mounted onan appropriate turntable;

FIG. 2 is a fragmentary representation of the disc shown in FIG. 1, onan enlarged scale;

FIG. 3 is a side section of the disc of FIG. 1, taken essentially alongthe line 3--3 of FIG. 1;

FIG. 4 is a section of the disc shown in FIG. 2, taken along the line4--4 of FIG. 2;

FIG. 5 is a schematic representation showing the manner in which theimpressions from a master die may be embossed into the surface of thedisc record shown in FIGS. 1-4; and

FIGS. 6A and 6B show various steps in which a surface opaque layer maybe deposited over selected portions of the embossed disc record.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

The apparatus shown in FIG. 1 includes a video disc record 10 which maybe constructed in accordance with the concepts of the present invention,and which has video signals optically recorded thereon. The videosignals are recorded on the disc 10, as will be described, in arecording track which extends as a micro-spiral from the outer peripheryof the disc towards its center. The recording track on the disc 10 mayhave a width, for example, of the order of 1 micron, and the spacingbetween adjacent convolutions of the disc may also be of the order of 1micron.

As shown in FIGS. 2 and 4, the spiral recording track is formed in aplanar surface of the disc 10 as a sequence of spaced, discontinuousmicrogrooves 22. The successive microgrooves have constant widths andconstant depths and have continuously-variable lengths representative ofthe recorded video signals. High relief areas 20 of the disc surface arelocated circumferentially between the successive microgrooves 22, andhigh relief intertrack portions 24 of the disc surface are locatedradially between adjacent convolutions of the spiral recording track.The successive high relief areas 20 are coplanar with the successivehigh relief intertrack portions 24. The successive microgrooves 22 andhigh relief areas 20 are also referred to as first and second regions,respectively.

The video recording disc 10 is supported on a turntable 11 which, inturn, is rotatably driven by an electric motor 12. The motor 12 mayrotate the turntable at a relatively high speed, for example, in therange of 900-3600 rpm.

The disc 10 may have a cross sectional configuration as shown, forexample, in FIG. 3. A metallic deposit is placed over portions of theupper surface of the disc 10, as designated 13 in FIGS. 2 and 4. As willbe described, the disc 10 may have a laminated structure, shown in FIG.4, to be composed of a first portion 10a of a relatively hardtransparent plastic, such as polyvinyl chloride; whereas the upperportion 10b may be of a relatively soft transparent plastic which may besuitably emobssed with the aforesaid micro-grooves when the aforesaidalternate procedure is followed. The disc 10 may include a portionsimilar to the portion 10b of its opposite side, and so as to constitutea two-sided record, as described in the copending application Ser. No.741,020, filed June 28, 1968, and now U.S. Pat. No. 3,530,258.

The metallic deposit 13 is selectively placed on the high reliefportions of the surface of the layer 10b, after the surface has beenembossed, so that the video recordings appear as discontinuousmicro-grooves in which the transparency is retained, and which extendalong a spiral recording track.

FIG. 2 shows the high relief regions at 20, the grooves at 22 and thespacing between adjacent convolutions at 24. A high relief region 20 isalso referred to as a land or a first region. A groove 22 is alsoreferred to as a discontinuity or a second region. A spacing 24 betweenadjacent convolutions is also referred to as an intertrack region. Byinspection of FIG. 2, it can be seen that the grooves 22 or secondregions are variable in length so as to modulate an impinging light beamwith the information recorded on the videodisc 10.

FIG. 4 shows that a pair of intertrack regions, shown generally at 24,are coplanar with a first region, shown generally at 20.

As mentioned above, the duplication process contemplated, by whichplastic record discs are formed on a mass production basis from a masterdie, is one in which embossing or stamping may be used. In carrying outthe embossing process, for example, and as shown in FIG. 5, a plasticblank disc 100 may be attached to a diaphragm 102 in a suitablecompartment 104.

The disc 100 may be constructed in the manner described above, so as tohave a surface layer of relatively soft plastic material. The disc 100in the chamber is then heated by any appropriate means to a criticaltemperature T1, which is such that the surface tension of the materialforming the surface layer of the disc 100 causes the surface to besmooth and regular, also referred to as planar.

A master embossing die 106 is also provided, and it is mounted in afixed position facing the plastic disc 100. The master die is thenheated to a temperature which is slightly above the aforesaid criticaltemperature. The diaphragm 102 is then moved by fluid pressure, or by aram, to bring the disc 100 against the embossing face of the master die106. The temperature of the die is cooled back to the criticaltemperature. When the pressure is removed from the diaphragm 102, theattached disc 100 is moved back from the die 106, with the impressionsof the die being embossed on the surface of the disc; but withoutcausing either abrasion of the embossing die, or loss of information dueto surface tension of the plastic material. The use of the diaphragm 102prevents any minute side motion between the disc 100 and the die 106, asthe disc is moved against the die, and vice versa.

If necessary, a slight vacuum pressure may be used at the end of theembossing operation to move the disc 100 back from the surface of thedie 106. In addition, or as an alternative, electrostatic means may beused, the diaphragm 102 and master die 106 being metal, to cause thesetwo members to move together and achieve the desired embossing action.For example, the master die 106 may be formed of tungsten steel, and thediaphragm 102 may be formed of nickel. Then, the two elements may becharged and discharged electrostatically, so as to bring the disc 100against the face of the die 106, and subsequently to move the disc awayfrom the die.

After the disc 100 has been embossed with the video information, forexample, by the duplication process and apparatus of FIG. 5, a metal, orother opaque mask, is deposited onto the surfaces above the embossedmicro-grooves which are formed in the surface of the disc. As mentionedabove, a method of achieving this is to use vacuum deposition and ashadow mask technique, as shown schematically in FIGS. 6A and 6B.

As shown in the schematic sketches of FIGS. 6A and 6B, the disc 100 isconsidered to be mounted on a suitable turntable in a vacuum depositionchamber. The source(s) of the radiated metal 131', such as aluminum,designated 200, is (are) offset from the center of the disc 100 andraised slightly above its surface, as shown. The angle formed betweenthe surface of the disc 100 and of the radiated metal is designated α inFIGS. 6A and 6B. If this angle is fairly small, then the radiated metalwill be formed on the upper sides of the embossed grooves, first on oneside as shown in FIG. 6A, and then continuously around the other side,as the record rotates, as shown in FIG. 6B. Therefore, as the metaldeposition process continues and as the record 100 rotates, a thincoating of metal will be formed over the top edges of the micro-grooves,and also on the upper lands and other high relief areas of the discsurface(s).

That is, if the disc 100 is held on a turntable, and if the turntableholding the disc is slowly turned, then on the first half revolution,and as shown in FIG. 6A, all the inside edges of the grooves willreceive one coating of metal on the half furthest from the source. Then,when the record has gone through the next half revolution, both sides ofthe grooves will have received a continuous coating of metal around theedges of all the grooves, as shown in FIG. 6B. As the process continuesthrough several revolutions, the corners of the metal deposit sharpen,and provide a uniform opaque metal layer over the high relief areas ofthe disc surface. The process has the feature of increasing the opticalcontrast ratio by the presence of the metal, and by the fact that thegrooves themselves are not coated at their bottoms.

The optical contrast ratios refer to the levels of light provided by thefirst and second regions 20 and 22, respectively. The metal coveredregion 20 reflects more light than the uncovered region 22. Theuncovered region 22 transmits more light than the metal covered region20.

In the finished disc, the surface has, arranged in a concentric spiral,deformities or discontinuities which are out of the plane of the surfaceand which deformities or discontinuities modulate impinging radiantenergy to apply the information recorded on the disc to the radiantenergy.

While a particular structure and process has been described,modifications may be made. The following claims define the invention.

What is claimed is:
 1. A method for forming a plastic record disc havinga spiral-shaped recording track that includes a succession ofalternating regions of optical contrast having variable lengths, themethod comprising the steps of:providing a disc-shaped unitarystructural die member having a planar surface for carrying aninformation signal in an information track formed by a plurality ofcircumferentially spaced rasied members extending away from the plane ofthe planar surface and terminating in a common plane spaced from saidplanar surface, and wherein said information track is in the form of aspiral having a plurality of turns, each of said turns is separated froman adjacent one of said turns by an intertrack portion of said planarsurface, the information track includes a plurality of alternatelypositioned first and second regions arranged in sequential order, eachof said first regions is formed from a portion of said planar surfacesuch that each of said first regions is coplanar with said intertrackportions of said planar surface, each of said first regions is locatedintermediate two of said second regions, each of said second regions isdefined by one of said spaced members and formed with a constantdimension in the radial direction of the disc-shaped member and aconstant maximum dimension in the direction perpendicular to said firstsurface, and each of said second regions is formed with a variablelength representative of the information signal; heating said diemember; moving a body of heated plastic into compressive engagementagainst said die to form a record disc having a planar recording surfacewith a spiral-shaped recording track that includes a succession ofalternating regions of optical contrast having variable lengths; coolingthe die during said period of compressive engagement such that therecord disc retains the recording track in the disc when removed fromsaid die; and releasing said compressive engagement.
 2. The method forforming a record disc as recited in claim 1, wherein:said heating stepheats said die to a temperature below the melting point of the plasticmember, but above a temperature at which plastic flow of the member canoccur.
 3. A method for forming a plastic record disc having aspiral-shaped recording track that includes a succession of alternatingregions of optical contrast having variable lengths, the methodcomprising the steps of:attaching a heat softable blank to a movablemember, said member holding said blank in spaced relationship to a die,the die carrying a recording track complementary to that of a plasticrecord disc to be formed; heating the blank to a temperature to rendersaid blank embossable; moving the blank into compressive engagement withthe die by moving said member to form a record disc having a planarrecording surface with a spiral-shaped recording track that includes asuccession of alternating regions of optical contrast havingcontinuously variable lengths; cooling the record disc such that therecording track is retained in the disc and releasing said compressiveengagement.
 4. The method as defined in claim 3, wherein the step ofheating is accomplished by heating the die.
 5. A method as defined inclaim 4, wherein:the step of heating raises the plastic body to atemperature less than its melting temperature; and the record disc isformed without any transverse melt flow of plastic material.
 6. A methodfor embossing a spiral-shaped recording track in a plastic record disc,comprising steps of:positioning a plastic, disc-shaped record blank inspaced parallel relationship to a disc-shaped die, the die carrying aspiral-shaped recording track having a shape complementary to that to beembossed in the record blank; heating the record blank to a temperaturebelow its melting temperature; moving the heated record blank intocompressive engagement with the die, to emboss a spiral-shaped recordingtrack in the blank and thereby form a record disc having a recordingtrack that includes a succession of spaced microgrooves having variablelengths; cooling the record disc, whereby the recording track isretained therein; and releasing said compressive engagement andreturning the cooled record disc to a position spaced from the die.
 7. Amethod as defined in claim 6, wherein the step of heating isaccomplished by heating the die.
 8. A method as defined in claim 6,wherein the step of cooling is accomplished by cooling the die.
 9. Amethod as defined in claim 7, wherein the spiral-shaped recording trackis embossed in the record blank without any transverse flow of plasticmaterial.
 10. A method for embossing a spiral-shaped recording track ina plastic record disc, comprising steps of:positioning a plastic,disc-shaped record blank in a spaced parallel relationship to adisc-shaped die, the die carrying a spiral-shaped recording track havinga shape complementary to that to be formed in the record blank; heatingthe record blank to a temperature below its melting temperature; movingthe heated record blank into compressive engagement with the die, toform a spiral-shaped recording track in the blank and thereby form arecord disc having a recording track that includes a succession ofspaced microgrooves having continuously-variable lengths; cooling therecord disc, whereby the recording track is retained therein; andreleasing said compressive engagement and returning the cooled recorddisc to a position spaced from the die.
 11. A method as defined in claim10, wherein the step of heating is accomplished by heating the die. 12.A method as defined in claim 11, wherein the spiral-shaped recordingtrack is embossed in the record blank without any transverse melt flowof plastic material.
 13. A method for forming an information storagemember of the type having information signals optically representedthereon in the form suitable for sensing by an impinging light beam,comprising the steps of:providing a unitary structural member for use asan information storage member having a first surface to carry theinformation signals; forming an information track as a spiral-shapedtrack having a plurality of turns in the spiral, and further formingsaid information track such that each of said turns is separated from anadjacent one of said turns by an intertrack portion of said firstsurface, and further forming said spiral track using a plurality ofalternately positioned first and second regions arranged in sequentialorder; constructing each of said first and second regions to providecorresponding first and second levels of light therefrom, respectively,in response to an impinging light beam; forming each of said firstregions from a portion of said first surface such that each of saidfirst regions is planar in shape and coplanar with said intertrackportions of said first surface and one of said first regions beinglocated intermediate two of said second regions; forming each of saidsecond regions as a discontinuity extending out of the plane of saidfirst region; forming each said discontinuity with a substantiallyconstant dimension in the radial direction of the disc-shaped record andforming each of said discontinuities so as to have bottom whichtermintes within said member; and forming said discontinuities with avariable length, thereby forming a video disc having successive firstand second regions capable of modulating a light beam so as to representthe information optically recorded thereon.
 14. A method for forming aninformation storage member of the type having information signalsoptically represented thereon in the form suitable for sensing by animpinging light beam, comprising the steps of:providing a unitarystructural member for use as an information storage member having afirst surface to carry the information signals: forming an informationtrack in the form of a spiral-shaped track having a plurality of turnsin the spiral, and further forming said information track such that eachof said turns is separated from an adjacent one of said turns by anintertrack portion of said first surface, and further forming saidspiral track using a plurality of alternately positioned first andsecond regions arranged in sequential order; constructing each of saidfirst and second regions to provide corresponding first and secondlevels of light sensed therefrom, respectively, in response to animpinging light beam; forming each of said first regions to be lightreflective, and further forming each of said first regions from aportion of said first surface such that each of said first regions isplanar in shape and coplanar with said intertrack portions of said firstsurface, and one of said first regions being located intermediate two ofsaid second regions; forming each of said second regions to be of lowerlight reflectivity than the level of reflectivity from said firstregions, and further forming each of said second regions as adiscontinuity extending out of the plane of said first regions; formingeach said discontinuities with a substantially constant dimension in theradial direction of the disc-shaped record and forming each of saiddiscontinuities so as to have a bottom which terminates within saidmember; and forming said discontinuities with variable length, therebyforming a video disc having successive first and second regions capableof modulating a light beam so as to represent the information opticallyrecorded thereon.
 15. A method for forming an information storage memberof the type having information signals optically represented thereon inthe form suitable for sensing by an impinging light beam, comprising thesteps of:providing a unitary structural member for use as a storagemember having at least a first surface to carry the information signals;forming an information track in the form of a spiral-shaped track havinga plurality of turns in the spiral, and further forming said informationtrack such that each of said turns is separated from an adjacent one ofsaid turns by an inter-track portion of said first surface, and furtherforming said spiral track using a plurality of alternately positionedfirst and second regions arranged in sequential order; constructing eachof said first and second regions to provide corresponding first andsecond levels of light sensed therefrom, respectively, in response to animpinging light beam; forming each of said first regions from a portionof said first surface such that each of said first regions is planar inshape and coplanar with said intertrack portions of said first surface,and one of said first regions being located intermediate two of saidsecond regions; forming each of said second regions as a discontinuityextending out of the plane of said first regions; shaping each of saiddiscontinuities to terminate within said member; providing each saiddiscontinuity with a substantially constant dimension in the radialdirection of the disc-shaped record; and forming said discontinuitieswith variable length, thereby forming a video disc having successivefirst and second regions capable of modulating a light beam so as torepresent the information optically recorded thereon.
 16. A method forforming an information storage member of the type having informationsignals optically represeented thereon in a form suitable for sensing byan impinging light beam, comprising the steps of:providing a unitarystructural member for use as an information storage member having atleast a first surface to carry the information signals; forming aninformation track in the form of a spiral-shaped track having aplurality of turns in the spiral, and further forming said informationtrack such that each of said turns is separated from an adjacent one ofsaid turns by an intertrack portion of said first surface, and furtherforming said spiral track using a plurality of alternately positionedfirst and second regions arranged in sequential order; constructing eachof said first and second regions to provide corresponding first andsecond levels of light sensed therefrom, respectively, in response to animpinginglight beam; forming each of said first regions to be lightreflective and further forming each of said first regions from a portionof said first surface such that each of said first regions is planar inshape and coplanar with said intertrack portions of said first surface,and one of first regions being located intermediate two of said secondregions; forming each of said second regions to be of lower lightreflectivity than the level of reflectivity from said first regions andfurther forming each of said second regions as a discontinuity extendingout of the plane of said first regions; forming each of saiddiscontinuities so as to have a bottom which terminates within saidmember; forming each said discontinuity with a substantially constantdimension in the radial direction of the disc-shaped record; and formingsaid discontinuities with a variable length, thereby forming a videodischaving successive first and second regions capable of modulating a lightbeam so as to represent the information optically recorded thereon. 17.A method for forming a plastic record disc having a spiral-shapedrecording track that includes a succession of alternating regions ofdifferent optical contrast having variable lengths, the methodcomprising the steps of:providing a disc-shaped unitary structural diemember having a substantially planar surface formed with a plurality ofseparate, discrete, successively positioned, and discontinuousdeformities departing directly from said planar surface, saiddeformities defining projections terminating in a common plane displacedfrom said planar surface, said deformities being arranged in a spiraltrack, with undisturbed planar surface portions surrounding each of saiddeformities; heating said die member; moving a body of heated plasticinto compressive engagement with said die member to form a record dischaving a substantially planar surface formed with a plurality ofseparate, discrete, successively positioned, and discontinuousdeformities departing directly from said record disc planar surface,said deformities in said record disc defining depressions terminating ina common plane displaced from said record disc planar surface, saidrecord disc deformities being formed in a spiral track with undisturbedrecord disc planar surface portions surrounding each of said record discdeformities; releasing said compressive engagement; and depositing anopaque coating on at least said planar surface to produce aspiral-shaped recording track having a succession of alternating regionsof optical contrast and variable lengths.
 18. A method for forming aplastic record disc having a spiral-shaped recording track that includesa succession of alternating regions of different optical contrast havingvariable lengths, the method comprising the steps of:providing adisc-shaped unitary structural die member having a substantially planarsurface formed with a plurality of separate, discrete, successivelypositioned, and discontinuous deformities departing directly from saidplanar surface, said deformities defining projections terminating in acommon plane displaced from said planar surface, said deformities beingarranged in a spiral track, with undisturbed planar surface portionssurrounding each of said deformities; heating said die member; moving abody of heated plastic into compressive engagement with said die memberto form a record disc having a substantially planar surface formed witha plurality of separate, discrete, successively positioned, anddiscontinuous deformities departing directly from said record discplanar surface, said deformities in said record disc definingdepressions terminating in a common plane displaced from said recorddisc planar surface, said record disc deformities being formed in aspiral track with undisturbed record disc planar surface portionssurrounding each of said record disc deformities; cooling the die duringsaid period of compressive engagement such that the record disc retainsthe recording track in the disc when removed from the die; and releasingsaid compressive engagement.